Shown in FIG. 1 is a typical ignition distributor of the conventional type. In FIG. 1, a numeral 1 denotes a housing of the ignition distributor, numeral 2 denotes a cap connected to the housing 1, numeral 3 denotes a shaft adapted to be rotated by an internal combustion engine, numeral 4 denotes a spark-advance sleeve into which the shaft 3 is loosely fitted, numeral 5 denotes a reluctor provided on the spark-advance sleeve 4 and cooperating with a stator 6 to detect an ignition timing, numeral 7 denotes a magnet signal type generator for generating an ignition signal for each of the cylinders of an engine and numeral 8 denotes an ignition-timing control unit for processing the ignition signal generated by the magnet signal type generator 7 in response to the close relationship between the reluctor 5 and the stator 6.
A numeral 9 denotes a centrifugal spark-advance controller comprising a governor base 91 fixed to the shaft and weights 92 carried on the governor base 91 by means of weight holding pins 95 (see FIG. 3). Each of the weights 92 is engaging with a centrifugal spark-advance plate 94 through a spark-advance pin 96 provided for each of the weights 92.
Fixed to the governor base 91 by way of rivets 50 is a reluctor 10 for discriminating between the cylinders of an internal combustion engine, which rotates with the shaft 3 and cooperates with a sensor 11 that generates a signal for discriminating between the cylinders of an internal combustion engine in response to the rotation of the reluctor 10, in other words, in response to the rotation of the shaft 3. The sensor 11 is attached to the outer circumferential surface of the housing 1 in such a manner that the sensing surface 111 of the sensor 11 is exposed in the housing 1 and that the work end 100 of the reluctor 10 passes by the exposed sensing surface 111.
As shown in FIG. 2, the reluctor 10 has two openings 101 therein through which the rivets 50 extend such as to fix the reluctor 10 to the governor base 91 so that the reluctor 10 rotates with the governor base 91 in response to the rotation of the shaft 3. The reluctor 10 also has an unloaded opening 102 therein through which the weight holding pin 93 extends, as shown in FIG. 3.
In an engine having four cylinders, the shaft 3 makes one rotation for every two rotations of a crank shaft (not shown) of the engine and four ignition signals are output and one cylinder discriminating signal is output during each rotation of the shaft 3. Detection of a reference cylinder is achieved by using the cylinder discriminating signal from the sensor 11 and on the basis of the result of this detection, a signal is supplied to a fuel injecting device to inject fuel to the corresponding cylinder when the valve thereof is opened.
The conventional ignition distributor described above suffers from the following problems. In the conventional ignition distributor, the reluctor 10 is arranged to be biased away from the rotational axis, which results in affecting the concentration of the rotational movement of the shaft 3. Consequently, the bearings of the housing 1 supporting the shaft 3 are subjected to wear to a significant extent.
Furthermore, the rivets 50 are needed in the conventional ignition distributor in order to fix the reluctor 10 to the governor base 91, which causes an increase in the number of parts required to construct the product.